Nonhuman primates are frequently used in several areas of biomedical research. Despite their frequent utilization, however, several primate species require a genetic characterization for the establishment of adequate comparisons with the human and for their standardization as reliable animal models. The study of the genome organization of the nonhuman primates has been approached by karyological studies of genera in which fragmentary data are available. Very limited data are presently available on gene assignment in the nonhuman primates. Comparative gene maps are available for only 12 species in which the number of mapped genes ranges from a minimum of 25 to a maximum of 65. This contrasts strikingly with the human in which the known number of structural loci and anonymous gene sequences amounts to some 5000 markers. reason, a hybrid cell panel has For this been constructed for the New World spider monkey species, Ateles paniscus (2n=34) using a rodent receptor cell line and a donor primate fibroblast cell line. Contrary to what has been found in man and other mammals, comparative gene assignments of non-mammalian vertebrates have been hampered, largely due to technical impediments. For example, tissue culture technology is largely undeveloped outside of mammals. The present study proposes to construct a gene map of the African-clawed frog, Xenopus laevis, using a somatic cell genetics approach. This species is one of the most highly developed model systems in terms of the molecular biology of development, yet is relatively unstudied genetically. By better understanding gene expression and regulation in development, we should be better-suited to address normal and abnormal gene expression in cancer cells and in general.